A headrest prevents among other things, in case of a rear end vehicle collision, the head of a vehicle occupant from being jolted to the rear relative to the vehicle. Usually, headrests are insertable and height-adjustable in the backrest. In addition, there are headrests which are configured as an elongated, fixed part of the backrest of the vehicle seat. As regards the headrests currently existing in vehicles, irrespective of whether the headrests concerned are adjustable or non-adjustable, in the case of rear end collision the cervical vertebra of the vehicle occupant is exposed to high loads because the distance of the head from the headrest despite the back being in contact with the backrest may be relatively large (up to 160 mm).
To prevent these loads it has already been proposed to accommodate a small air bag in the headrest. In case of a collision a gas generator is activated via a sensor to fill the air bag within a few milliseconds. Since, however, the distance of the head from the air bag may differ very greatly, the head, for instance in the case of a very small head/headrest distance, would even be bumped by the air bag which constitutes an undesirable load.
Means have also been proposed which, in case of a collision, correct support for the head via spring stored energy or pyrotechnical means via a corresponding activation means so that on head contact the support instantly remains in position in each case. For control, corresponding sensors are arranged on the surface of the head support. Although the thus created means has achieved very positive results in testing, it has not gone into series production because of the high technical expense involved therein.